The proposed research is directed towards understanding the molecular basis of cannabinoid activity. Cannabinoids and other cannabimimetic agents produce a complex pattern of pharmacological actions some of which are believed to be related to their effects on cellular membranes while others are thought to be produced through an interaction with cannabinoid receptors, two of which have already been identified (CB1,CB2). The work to be carried out under the auspices of this award in involves a multifaceted approach to gain information on the molecular features required for the different types of cannabinoid activity within the known cannabimimetic structures. With regard to the membrane related cannabinoid effects, we will focus on carefully selected groups of structurally related analogs covering a wide range of potencies from each of the known cannabimimetic classes and study: (a) their conformational properties in solution and in membrane-like environments using state of the art 2-dimensional multinuclear NMR in combination with computational methods; (b) the orientation of these molecules in model and biological membranes using 2/H-solid-state NMR; (c) their location and conformation in the membranes using small angle X-ray and neutron diffraction; (d) their local environment in the membranes using high resolution NMR techniques for solids. To probe the stereoelectronic requirements of the cannabinoid receptors we plan to synthesize conformationally and electronically defined analogs. To obtain information on the molecular features of the cannabinoid receptor sites and the manner with which the different ligands interact with these sites we plan to synthesize suitable covalent ligands. These will be used to label or radiolabel cannabinoid receptor clones or mutants in an effort to determine the amino acid residues with which the ligand interacts. The biochemical and pharmacological properties of all analogs will be studied to determine their usefulness as receptor probes or drug prototypes. The information obtained from our studies will be used for the design and synthesis of novel cannabimimetic agents possessing high potency and selectivity. Such agents could be therapeutically useful as non-opioid analgesics, new drugs against glaucoma or as immunomodulatory agents.